An enhanced version of picady, a computer program which models capacities, queues and delays at major/minor junctions, is described. The program uses empirical formulae as a basis for the calculation of capacities and time-dependent queueing equations for queue and delay predictions. The enhancements include the facility (i) to model four-arm junctions, i.e. crossroads, left-right and right-left staggers, (ii) to predict geometric delays and (iii) to include the effects of pedestrian (zebra) crossings adjacent to the junction. Flared minor roads and the effects of major road right-turning traffic blocking through traffic are also dealt with. The enhancements result from recent empirical and analytical studies. Additionally, the flexibility of the program (now known as picady2) has been increased, with the availability of micro-computer and interactive versions. User inputs consist of various geometric characteristics of the junction, and traffic (and pedestrian) demand flow information (which may be specified in a number of ways). peak periods are usually modelled and capacities, queues and delays are calculated for each non-priority traffic stream for each of a succession of short time segments (usually 10 or 15 minutes) within the period. The user is able to assess the performance of both planned and existing layouts in terms of queueing delay and geometric delay. Details of the required input parameters are given, the output is described and a full example is included. (Author/publisher)
Abstract